In prior art disk drives, the disk(s) are conventionally hard mounted to a hub, as seen in FIGS. 1 and 2, of U.S. Pat. No. 3,587,074 to A. M. Angle et al; or to a motor rotor as seen in FIG. 1, the prior art, of U.S. Pat. No. 4,945,432 to T. Matsudaira et al, and FIG. 1 of U.S. Pat. No. 4,965,476 to J. G. Lin. In all such hard mounted hard disk assemblies, the motion of the power train which drives the hard disk or disks, induces unwanted disk motion which adversely affects the read/write function of the head/disk assembly.
The thrust of the teachings of Matsudaira et al, as to their invention, is to provide an axially compliant mount for fragile disks in a disk stack so that the "--magnetic disks 1 are protected against extraordinarily large forces caused by the difference in thermal expansion of different components. Thus, the disks are not deformed and do not break." (column 4, lines 31-33 of Matsudaira et al).
Matsudaira et al, in FIG. 2, for example, illustrate a disk assembly, such as an assembly of ceramic or glass disks, in a disk stack on the hub of a motor rotor. The disks in the disk stack are spaced apart by elastic spacers and clamped in a stack between a shoulder 10 at the bottom of the motor hub or spindle and a clamp secured at the upper end of the motor hub.
In small form factor disk drives, the mounting of the disk is critical. Disk flatness requirements in small form factor disk drives frequently are much tighter than acceptable tolerances in larger drives. Soft mounts for individual disks, as taught by Matsudaira et al, are unacceptable. As seen in FIG. 1, the prior art, in the present application, which illustrates a small form factor memory disk assembly 8, say, of the order of 1.3 form factor, a hard disk pack 3 comprising a disk support ring 3a, functioning both as a disk mount and a disk spacer ring, is provided with coaxial, flat, annular, axial surfaces, 3b, 3c, to which the hard disks, 3d, 3e, are adhesively bonded. This is a hard mount of the hard disks, 3d, 3e. The adhesive bonding is the sole support of the hard disks, 3d, 3e, in the hard disk pack 3. Inner annular coaxial surfaces, 3f, 3g, of the hard disk support ring 3a of the hard disk pack 3, provide hard mounting surfaces for the hard disk support ring 3a of the hard disk pack 3, on a cylindrical section 5a of the motor rotor 5 which powers the disk pack 3. The disk pack 3, as used here, may comprise only one disk 3d, but the requirement of a hard flat mount for warp-free mounting of that single disk 3d remains.
The disk support ring 3a of the hard disk pack 3 provides a sturdy mount for attachment to the cylindrical section 5a of the motor rotor 5. Thus, when the inner annular axial surfaces, 3f, 3g, of the disk support ring 3a are subject to clamping pressure between a shoulder 5b on the cylindrical section 5a on the motor rotor, and a clamp 5c at the end of the cylindrical section 5a, there is no distortion of the disk support ring 3a of the disk pack 3 at least, in the region where the disks are bonded, to distort or warp the disks, 3d, 3e, bonded thereto. But this is a hard mount of the disk spacer ring 3a, and, while it is an ideal mount for the small thin fragile disks, it also transmits motion, other than rotation, from the power train of the hard disk assembly to the disk pack 3 and to the disks, 3d, 3e.
This is acceptable for certain track and bit densities on the hard disks, but the pressure to increase data storage without increasing storage volume, indicates the need to minimize unwanted disk motion. The teachings of the prior art referenced above, indicate no awareness of the undesirable effects of unwanted disk motion, indicate no awareness of the problem associated with and causing that undesirable condition and suggest no solution to that problem, either directly, by implication, or by accident.